This invention relates to a small personal type watercraft and more particularly to an improved engine control for such a type of watercraft.
The field of so-called "personal watercraft" is one that is growing rapidly. However, due to the large number of such watercraft, there is a concern for improving environmental protection by implementing engine controls for such watercraft. In many instances, catalytic treatment is desirable for the watercraft engine, particularly when the engine is of the two-cycle, crankcase compression type.
Because of its very nature, however, the small confined space available for the propulsion unit in such watercraft gives rise to certain problems. As is well known, the catalyst must be at or above a specific temperature in order to operate efficiently. However, under some operating conditions, the temperature of the catalyst may become quite elevated, particularly when large amounts of exhaust gases having high amounts of unburned hydrocarbons must be treated. This provides certain problems in connection with heat control.
Although the heat or temperature of the catalyst can be controlled and is controlled by water-jacketing the catalyst, too high a cooling of the catalyst can result in its operation at temperatures less than those required in order to be effective. Thus, the amount of cooling provided should be limited so as to avoid over-cooling of the catalyst. This further aggravates the problem of preventing excess temperatures.
It is, therefore, a principal object of this invention to provide an improved control arrangement for the engine of a personal watercraft having a catalytic converter.
It is a further object of this invention to provide an improved catalytic converter control arrangement for a personal watercraft wherein overheating conditions can be avoided.
It may be desirable in order to provide effective control to incorporate an arrangement wherein the engine of the watercraft is slowed or stopped if the temperature of the converter becomes too high. However, merely stopping the engine does not totally avoid these potential problems.
For example, the watercraft may be shut down and then the operator can again restart the watercraft engine. Since starting techniques frequently provide richer than normal mixtures, further aggravation of the overheated condition of the catalyst can occur if the engine is started again too soon after shutdown.
It is, therefore, a further object of this invention to provide an improved temperature control system for the catalytic exhaust of a personal watercraft wherein restarting of the engine after shutdown is not permitted until the catalyst reaches a safe temperature.
In conjunction with the shutting down of the engine to prevent damage due to catalyst overheating, if the engine is abruptly stopped, certain other ancillary problems may arise. Also, this may fail to give the operator warning of shutdown among other problems.
It is, therefore, a further object of this invention to provide an improved shutdown procedure for a catalytic exhaust system of a personal watercraft.